Combination drilling bit



Jan. 7, 1958 H. I. HENDERSON 2,819,043

COMBINATION DRILLING BIT Filed June 15, 1955 m fifi y j N A? l 36 a N M I! Z ,7 Z

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United States Patent 1 2,819,043 COMBINATION DRILLING BIT Homer I. Henderson, San Angelo, Tex. Application June 13, 1955, Serial No. 515,131

3 Claims. (Cl. 25561) My invention relates in general to drilling bits and more particularly to drilling bits adapted for earth boring drills. Still more particularly the drilling bit of my invention is a combination of two types of bits, combining (one) an abrading type bit, often referred to in the art as a diamond bit with (two) a cutting blade bit, often referred to in the art as a drag bit or fish tail bit."

An object of the invention is to provide a diamond type bit with cutting blades so that the bit will not be incapacitated when the bit drills into a soft or sticky formation. Conventional diamond bits are well adapted for drilling relatively hard formations but are practically useless in relatively soft formations; this characteristic necessitates frequent and costly replacement of drill bits when drilling in areas of hard formations which are separated by soft formations. The bit of my invention drills both hard and soft formations with good efficiency.

A further object of this invention is to provide a combination diamond and drag bit with provision for the drag bit cutting blades to be retracted only when drilling hard formations and further to be so retracted that the said cutting blades will be self-sharpening when in the retracted position.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings, in which:

Figure 1 is a longitudinal view, partly in section, of the drilling bit of this invention, mounted on the lower end of a drill pipe such as is used in reverse circulation drilling.

Figure 2 is a cross-sectional view taken along the line 22 of Figure 1, showing two drag type cutting blades, one in the up position and one in the down position.

Figure 3 is a plan view of the bit, looking upwardly from below the bit as shown in Figure 1.

Figure 4 is a cross-sectional view taken along the line 44 of Figure 2, and showing the contour of the diamond section of the bit.

With reference to the drawing, the invention is illustrated as being incorporated with a drill pipe, and adapted to be rotated thereby.

Figure 1 shows an embodiment adapted to be used for core drilling in conjunction with reverse circulation drilling. For reverse circulation the drill pipe actually comprises two pipes, an outer pipe 1th, and an inner pipe 11. The bit body 12, is threaded to engage the threaded end of the drill pipe at 13. The ring seal 14, effects a seal between the bit body 12, and the inner pipe 11. The bit mounts diamonds 15, on the cutting surface in a conventional manner. Carbide chips may be used in lieu of diamonds, but generally the more expensive diamonds are preferable. The contour of the diamond portion of the bit may be as shown in Figure 4, which contour is conventional, except for the substantially full hole body above the diamonds as shown at 16, in Figure 1 and Figure 4. This full hole body is used in reverse circulation to constrict the drilling fluid passage-way between the bit and the bore of the hole so that most of the drilling fluid will be forced to go into the inner pipe 11. The arrows 17, show the direction of the flow for the drilling fluid.

It frequently happens in well drilling, that an exceedingly hard rock formation makes it desirable to drill with a diamond bit, and a diamond bit is so mounted. After drilling a few feet the bit may gofrom very hard ICC formation to a soft formation in which the diamond bit is very ineffective. This may make it necessary to withdraw the drill pipe, an expensive operation, to replace the diamond bit with a drag bit which is adapted for drilling soft formations. Upon drilling in the soft formation for a few feet the drill may again encounter a very hard formation that cannot be cut by the drag bit, thus necessitating another replacement of drilling bits, and so on.

One of the objects of this invention is to provide a diamond bit with drag bit cutting blades, and so constructed that the bit can effectively cut hole either as a diamond" abrading bit or as a drag cutting bit. To provide for the mounting of the drag cutting blades, the bit body 12, is recessed as at 18. At the upper end of the recess i8, is a slot 19. The slot 19, is of proper thickness and width to tightly fit the upper end of the cutter blade 20. The cutter blade 20, is contoured to fit the contours of the bit body 12, and to tightly fit in the slot 19. The upper end of the cutter blade 20, has two holes 21, to receive the studs 22, of the cap screws 23. Holes 24, are drilled and tapped in the bit body 12; these holes are of proper size to receive the cap screws 23, and are positioned so that the studs 22, of the cap screws 23, will engage the holes 21, in the cutter blades 20. The purpose of the screws 23, with studs 22, is to bind and hold the cutter blades 20, in place. The threaded holes 24, are shown drilled from the center of the bit toward the periphery, but those skilled in the art will recognize that these threaded holes might just as well be drilled from the periphery, inwardly, to accomplish the same purpose. The blade 20, may be made of spring steel; and brazed (or otherwise fastened) to the outer end is a cutting head 25. This cutting head may be made of tungsten carbide or other very hard material, adapted for cutting, and it is ground to present an eflicient cutting tool to the formation to be drilled, that is, the cutting head has the correct clearance angle and cutting angle. This cutting head is also ground to fit the contour of the floor of the hole, as left by the diamond bit, which may be as shown in Figure 4. The spring blades 20, are of such design that the normal drilling load on the bit will deflect the blade 20, together with head 25, upward into the recess 18, when the floor of the hole is a hard formation. in Figure 1, the blade 20 is shown by dotted lines deflected up ward into the recess 18. When the blade 20, is in this position the formation is hard and the bit cuts as a diemond bit. It will be noted that when the blade 28, swings through an arc to the up position, the heel 26, of the head 25, is resting on the hole floor and the cutting edge of the head 25, is above the hole floor and is protected from wear; actually when in the up position the head 25 is self-sharpening. Those skilled in the cutting tool art will note that when the cutting head is in the up position the cutting head actuaiiy has a negative clearance angle since the heel of the bit is riding on the work, forcing the cutting edge to ride above the work. Within the recess 18, is secured a blade stop 27, against which the blade 2i), rests when in the down position. On the side of the recess 18, opposite the stop 2.7, is secured a bar 28. The purpose of the bar 23, is to restrict the throat of the recess 18, so that the most narrow place of the recess is at the throat entrance at the very base of the bit, which insures that any cutting, or debris, that clears this throat will have clearance elsewhere in the recess and will be flushed out of the recess, and into the inner pipe 11, and hence upward to the earths surface.

One method of computing the strength of the spring blades 20 (or the weight to put on the bit) is as follows:

(1) Let the optimum weight on the diamond bitbe W;

(2) Design the blades 20, so that the weight W/2 deflects all blades 20, into the up position.

(3) When drilling on hard formations the blades 2%, will support W/2, therefore the total weight on the bit should be W+W/2=3/2W.

When drilling on soft formation the blades 21), will spring downwardly and will slightly imbed the cutting head 25, into the soft formation. As the bit turns the cutting head 25, will be forced downwardly and backwardly until it comes to rest against the stop 27, at which point it will cut its thickest shaving B, which will by design clear the throat opening of width A. In the down position the cutting head has a positive clearance angle in that the cutting edge is biting into the Work and the heel is above the work, i. e. the heel has clearance. A zero clearance angle is permissible in some drilling conditions. Any excess weight on the bit during soft formation drilling will be taken by the large area of the bit body; however I normally prefer to reduce the weight on the bit when drilling in soft formations. it while drilling in soft formation the bit drills through to a hard formation, which the cutting heads 25, will not penetrate, then the spring blades 20, will be deflected upwardly into the recess 18, letting the diamonds come to bear on the hard formation, and the bit will again cut as a diamond bit. It will be obvious that the blades 20, could be rigid arms hinged at the upper edge of the recesses 18, with coacting springs to force them downwardly, but for simplicity applicant prefers to combine these two elements into a single dual-function element.

I may use several different channels for drill fluid circulation, as shown in the various views and by arrows 17. I prefer to bring fluid into the top of the recess 18, and impinge it upon the face of the head 25, this fluid flows through channels 29, 30 and 32. The channel 30 is drilled radially inward and the outer end subsequently plugged with plug 31. I also prefer to bring fluid into the lower portion of the recess 18, such as by the channel 34, leading from the channel 33. The channel 34, is drilled radially inward and the outer end plugged with plug 35. Also I may flute the drill body 12, as shown by flute 36, into which is channeled drilling fluid to lubricate the diamond bit and carry away the abraded cuttings. The flutes may be fed drilling fluid by the channels 37. Other means and routes for providing for drilling fluid circulation may be used without departing from the spirit of the invention.

Figure 2 shows one cutter blade 20a, in the down position and one cutter blade 2%, in the up position. It will be noted that the blades 20 are so cut as to have no peripheral clearance in the up position, in which position the blade is most extended; this results in the blade having a small amount of clearance in the down position as shown at 39 and 40, in Figure 2. This clearance results in a small amount of earth material being left uncut on the diameter of the core (larger) and the diameter of the bore hole (smaller), but this uncut material is trimmed to gauge by the diamonds when drilling in a soft formation.

It will be obvious to those skilled in the art that the core 38, may be varied in diameter, making it smaller, and smaller, until it becomes very small and fragile, whereupon it will break and crumble in the drilling fluid. When this small size of core is reached, this bit is no longer regarded as a core bit but is regarded as a fullhole bit.

To those skilled in the drilling art it will be obvious that this bit can be used with conventional circulation as well as with reverse circulation. The functioning ofthebit is not altered, only the sense of or direction of circulation is altered. Of course, if one uses a core bit, then the choice of the established methods of core recovery is to be used. This will be dictated by which method of circulation is to be used, i. e., reverse" or fconventional? It was expedient to show but two cutter blades in the drawings, but it will be obvious that more cutter blades could be used, three blades being often preferred, or even more.

It will be obvious to those skilled in the art that the spring pressed retracting cutter blade of this disclosure could be used in conjunction with roller type rock bits as well as with diamond type rock bits.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. A drill bit for rotary type earth boring adapted to be secured to the lower end of the drill pipe, and adapted for drilling either hard or relatively soft media, comprising, in combination, a bit body having an upper and a lower end and having spaced recesses projecting laterally and upwardly at a definite angle from the said lower end into said bit body, a spring having an upper and a lower end mounted in each recess, the upper end of said spring secured to the bit body at the top of said recess, the lower end of each spring projecting downwardly and out of the recess and slightly below the lower end of said bit body, a drag type cutting head adapted for cutting soft media integrally mounted on the lower end of each spring, each said spring adapted to be flexed upwardly by an upward force of a predetermined magnitude moving said drag type cutting head upward into said recess, chips of an extremely hard material mounted on the face of the lower end of said bit body and adapted for cutting hard media.

2. In a diamond type hard rock earth boring bit adapted to rotary type drilling, the improvement for adapting the bit for eflicient drilling of soft media as well as hard media, said improvement comprising, in combination, a bit body having an upper end and a lower cutting end, and having diamonds or similar hard chips mounted on the face of the lower cutting end, said body having spaced recesses projecting laterally and upwardly from said lower cutting end into said bit body, springs, each having an upper and a lower end, the said upper end adapted for securing to the bit body, a drag type cutting head integrally mounted on said lower end of each spring, one of said springs mounted axially within each recess by securing the upper end of said spring to the bit body at the top of said recess, the lower end of said spring mounting the said drag type cutting head projecting downwardly and slightly below said bit body lower cutting end, the strength of said spring being such as to force the drag type cutting head into soft formations, and such that when hard media are encountered the drag type cutting head will not penetrate the medium and the weight on the bit will force the said spring to flex moving the drag type cutting head upwardly into the said recess, permitting the diamond type bit to cut the hard medium unobstructed.

3. A drill bit according to claim 2, in which the drag type cutting head presents a positive clearance angle in the down position, and a negative clearance angle in the up position.

References Cited in the file of this patent UNITED STATES PATENTS 451,292 McKee Apr. 28, 1891 1,478,341 Grant et a1. Feb. 25, 1930 2,320,610 Kandle June 1, 1943 2,566,671 Livingstone Sept. 4, 1951 

